Hysteresis dynamoelectric machine



H. C. ROTES April 3, lss

HYSTERESIS DYNAMOELECTRIC MACHENE 2 Sheets-Sheet Filed Oci. 3l, 1945 INVENTOR HERBERT C. @07E/Q5 BY M6 ATTORNEY Patented Apr. 3, 1951 UNITEDVSTATES PATENT OFFICE HYSTERESIS DYNAMOELECTRIC MACHINE Herbert C. Roters, Kew Gardens, N. Y., assignor, by mesne assignments, to Casner Patents, Inc., New York, N. Y., a corporation of New York Application October 31, 1945, Serial No. 625,878

17 Claims. l

This invention relates to hysteresis dynamoelectric machines and, while it is of general applicaticn, it is especially adapted to fractional horsepower self-starting hysteresis motors of the synchronous and control or torque motor types. This application is a continuation-in-part of my copending application, Serial No. 521,650, filed February 9, 1944, entitled Alternating-Current Dynamoelectric Machine, now Patent 2,423,345, July 8, 1947, and assigned to the same assignee as the present application.

Fractional horsepower motors have a wide range of application in industrial and domestic appliances. In the past these motors have generally been of the direct-current or universal commutated-armature type or of the induction or synchronous types with distributed polyphase armature windings. The former type has the disadvantages of all commutator machines, namely, they are subject to wear and misadjustment of the commutator brushes and sparking at the commutator with the resultant wear and possible short circuiting of the commutator. In addition, they create troublesome high-frequency interference which is disturbing to radios and other domestic appliances. The latter type of prior art motor has had the disadvantage that, for a given power output, it has been of relatively large volume and weight and has been subject to high cost of manufacture, particularly in forming and placing the polyphase distributed winding. For example, in these small motors of the alternating-current type with internal slots, it has been customary to wind the coil in the open slots of the stator one turn at a time by threading the wire through the stator tunnel with a winding gun or by preforming the coil outside of the machine and inserting it in the slots one conductor at a time.

When such motors are operated as synchronous motors, it is important that they have a high synchronizing torque, since this parameter determines the maximum load which the motor can pull into synchronism, which is usually the limiting factor on synchronous motors.

On the other hand, in control motors or torque motors, it is customary to excite one phase winding continuously at substantially the rated voltage and to excite another phase winding with a control current of variable phase or of constant phase displacement and variable amplitude. It is essential that such motors have maximum sensitivity to energization of their control winding by control currents of relatively small phase displacement or of relatively small amplitude, or

both, and that such sensitivity be substantially uniform in all positions of the motor rotor.

In Patent No. 2,328,743, granted September 7, i943, on my application and entitled Self- Starting Hysteresis Motor, there is disclosed and claimed a self-starting hysteresis synchronous motor adapted for construction in fractional horse-power sizes by which the volume and weight of the motor for a given horsepower output may be substantially reduced. The present invention when applied to a motor of the type disclosed in the aforesaid patent provides an improved motor of such type which avoids both the use of a commutated armature and the forming and placing of the motor winding in a small armature tunnel, with the attendant disadvantages noted above, and which has maximum synchronizing torque when embodied in a motor to be operated synchronously and maximum and uniform sensitivity when operated as a control or torque motor.

It is an object of the invention, therefore, to provide a new and improved self-starting hysteresis dynamoelectric machine of improved and simplified construction resulting in a minimum size and cost for a given power rating.

It is another object of the invention to provide a new and improved self-starting hysteresis motor which is suitable for operation synchronously with maximum synchronizing torque.

It is another object of the invention to provide a new and improved self-starting hysteresis motor suitable for operation as a control or torque motor and having maximum sensitivity to controlling excitation which is uniform for all rotor positions.

In accordance with the invention, a self-starting hysteresis dynamoelectric machine includes cooperating stator and rotor members, one of the members comprising a magnetic core structure having a low conductivity to eddy currents and having a series of radially extending, angularly spaced winding slots and magnetic bridges for the ends thereof adjacent the other member and a polyphase distributed energizing winding disposed in the winding slots. The other of the members comprises a magnetic armature constructed at least in part of a magnetic material having a high hysteretic constant and the members have complementary cylindrical adjacent surfaces forming an air gap therebetween and have such relative diameters that the air gap is substantially the minimum permitted by manufacturing tolerances. The motor is further provided with means for mounting the members for relative rotation. The term cylindrical surface is used herein and in the appended claims to refer to surfaces of the type which is not necessarily a complete circular cylinder but which may be in the form of a salient pole surface the maior portion of which comprises segmental cylindrical surfaces.

In accordance with one embodiment oi the invention, a self-starting hysteresis motor comprises a stack of electrically insulated annular core laininations and one or more supporting bearing plates with external radial winding slots and a layer of thermoplastic adhesive nt-aterial interposed between adjacent laminations and betvveen such laminations and the end plates and constituting means for securing laininations and plates together Without substantially impairing their insulation to form a unitary core structure. This unitary core structure is provided with a, polyphase distributed energizing Winding disposed in the external Winding slots and a magnetic yoke is disposed about the core structure and the -winding. A supporting bearing is mounted from and supported by each oi the end plates and there is provided a cooperating rotor having a smooth cylindrical surface and disposed within the bore of the core structure and supported in the bearings and constructed at least in part of a magnetic material having a high hysteretic constant. ln a preferred i'orm of the invention the rotor is in the form of an annular shell of material having a high hysteretic constant and a central salient-pole core structure of high-permeability material.

By the terni external slots as used herein and in the appended claims is meant a slot which is open at 'the outer periphery of the magnetic core structure and is closed at the inner periphery thereof by a magnetic bridge.

For a, better understanding of the invention, together with other and further objects thereof, reference is had to the following description taken in connectionlvvith the accompanying drawings Whilel its scope will be pointed out in the appended claims.

Referring now to the drawings, Fig. lo is a longitudinal sectional View and Fig. lb an end view of an improved dynamoelectrio machine structure embodying the invention With the Winding omitted from lo for the sake of clarity;

lo is a view of a modified form of core lamination; Fig. 2 is a schematic circuit diagram illustrating the method connection of the windings of the motor of Figs. la and lb; Fig. 3 is a cross-sectional view or a stator structure similar to that of lo but slightly modiiied in detail; Fig. l is a cross-sectional view of a rotor designed to operate with the stator of Fig. 3; Fig. 6 is a cross-sectional View of a modified form of' rotor designed to operate with the stator of 1Eig. 3; while Figs. 5 and 7 are graphs repre-- senting operating characteristics of g, motor err-- bodying the invention and comprising the stator of Fig. 3 and the rotors of Figs. l and 6, respectively.

Referring now to Figs. lai, lb and ic of the drawings, there is represented a hysteresis dynamoelectric machine embodying the tion, which. is prefer lily constructed in accordance with the method described in my aforesaid copending application Serial No. 52l,650, or my copending application Serial No. 580,9G4, tiled Marc 19425, entitled Method of Manufacturing Dynamoelectric Machines, now Patent 2,483,024, September 27, i949, both assigned to the sam-e assignee as the present application.

This dynamoelectric machine comprises coopbetween t1 e adjacent iarninations and betweenr the laminations and plates, as by dipping them in a bath of such adhesive material, and euch adhesive material constitutes means for securing the laininatons and the end plates together to form a unitary magnetic core structure without substantially iin-pairing their insulation so that the structure has a low conductivity to eddy currents. rEhe adhesive material used for this purpose may be a polyvinyl-butyral resin or phenolic modification thereof or a copolymer oi vinyl acetate. and vinyl chloride and commercially available as Du Pont e624, Du Pont e631, Corde Adhesive and Bostik; or it may be furfural resin commercially available as Cyclevveld Cement.

or the core laminations ii has a series or". external radially-extending, angularly spaced Winding slots ila. The unitary core structure also has a series olf magnetic bridges for the ends ci the winding slots lia adjacent the rotor; specically the core laminations ii are formed with a conti nous inner bridge ring l lb. A conventional polyphase distributed energizing Winding i3 is disposed in the external Winding slots iis'. (omitted in lb for the sake of clarity) and may comprise any desired Winding pattern. rlhe motor also comprises an annular magnetic yol: ifi disposed about the unitaryA core structure. This yoie may comprise a series of annular laminations surrounding the core structure and the Winding i3. Mounted on the end plates I2, l2 and supported solely thereby are a pair of hubs or sleeves iti which can be attached to the end plates hy welding, brazing, or like process.

Alternatively the stator member comprising the stack ai laininations ii, the end plates i2, the winding and the yoke id may be assembled, as described, on a mandrel and, While so mounted, impregnated with a suitable insulating varnish or other coni-pound and baked. With such an assembly process, the insulating varnish forms a layer or" thermosetting adhesive between adjacent laininations and between the laminations and the end plates and serves with the Winding it and yoke iii to form a, rigid unitary stator structure.

The rotor il comprises a magnetic armature constructed at least in part oi a magnetic material having a high hysteretic constant. IThe motor also includes means for mounting the stator and rotor members or relative rotation; for example Within the ends of the sleeves i5 are mounted bearings iii, iii from which is supported the rotor il which is disposed Within the bor of the annular core structure, as indicated.

The unitary stator core structure described andthe rotor il are constructed with complementary smooth continuous cylindrical adjacent surfaces forming air gap therebetween and with such relative diameters that such air gap is substantially the minimum permitted by manufacturing tolerances. The moto structure as thus constructed may be inserted in any suitable protective housing not shown) which may serve also to carry the Winding terminals.

The armature teeth separating the radial external slots I Ia are shown iiared at the outer radius in order to provide a path of greater permeance for the ux between the core teeth and the yoke. However, if the iit between these parts is suiiiciently close, this flare may be eliminated by constructing the teeth as straight radial spokes, thereby providing a greater winding space, as illustrated in Fig. 1c.

With the dynamoelectric machine construction of the invention, it is possible to provide a multiple slot winding with each winding spanning several teeth. For example, in Fig. 2 there is represented schematically a circuit diagram of a two-phase motor constructed as described above having eight winding slots and eight windings, I-8, inclusive. As indicated, windings I, 2, 6 and 5, respectively, are connected directly across the supply terminals I8, while the windings 3, 1I, 8 and 1, respectively, are connected across the'supply terminals I8 through a phase-shifting condenser I9 to provide a uniform rotating magnetic iield. The several windings are disposed in the slots indicated in the following table:

Winding Slots I I and d 2 2 and 5 3 3 and 6 4 4 and I 5 5 and 8 6 6 and I 'I 'I and 2 8 8 and 3 Certain modiiications of the structure described above may be made while still realizing substantially the advantages enumerated above. For example, the stack of laminations II and end plates I2 may be held together by rivets, provided that they and the end plates are formed of high resistivity material to minimize eddy currents. Further the rotor I'I and its bearings I6, I6 may be mounted from theprotective housing, in case one is provided, instead of from the end plates I2, I2 as described. Also, while the stator laminations are shown as having eight winding slots and the motor wound as a two-phase eight-winding motor, it will be apparent that the number of winding slots may be any number appropriate to the type of winding and the number of poles and phases required.

'Ihe rotor of the invention may take a variety of forms such as illustrated and described in aforesaid Patent 2,328,743. The rotor of Figs. la and 1b is illustrated as being constructed in the form of an annular shell I Ia of a material having a high hysteretic constant, such as an aluminiumnickel-cobalt alloy commercially available as Alnico, surrounding a central portion IIb of low-permeability or non-magnetic material, such as stainless steel, which also serves as the motor shaft. The rotor including the portion I'Ib may be milled from a single rod, the portion I'Ia being cast in an annular recess formed therein, or the portion I'Ia and the end hubs of the rotor I'I may be formed separately and assembled in any suitable fashion on a continuous shaft of the size of the portion I'Ib.

In Fig. 3 is illustrated a stator structure having the same general constructional features of that of Figs. 1a and 1b but having different proportions suitable for a specific design described in detail hereinafter. The stator of Fig. 3 comprises a stack of electrically insulated annular core laminations 2I and may include end plates and bearing sleeves simila'i` to the plates I2 and bearing sleeves I5 of the structure of Figs. 1a and 1b. Each of the core laminations 2I has a series of external radially extending winding slots ZhiI and is formed with a continuous inner magnetic bridge ring 2| b. Any suitable polyphase distributed winding, not shown, is disposed in the winding slots 2Ia and the whole is surrounded with a magnetic yoke 24 which may itself com-A prise a stack of annular laminations closely t ting about the inner stack comprising the lamin nations 2|. The stator structure of Fig. 3 corresponds closely to the actual physical construc tion of one hysteresis motor embodying the invention.

A modified form of rotor is represented in Fig..

4. This rotor comprises a relatively thin annular shell 30 of a material having a high hysteretic constant, for example an aluminum-nickel-cobalty alloy, and a central salient-pole core 3i of highpermeability material, for example an SAE-1112 steel.

stator.

In Fig. 6 is illustrated a further modified form'` of rotor comprising a relatively thick annular shell 33 of material having a high hysteretic.l

constant, such as a cobalt alloy steel, and a cen--I tral core 34 of low-permeability or non-magnetici material, such as aluminum. This rotor is provided with a shaft 35 which may be similar to that of the rotor of Fig. 4, namely, stainless steel.

While the design constants of the dynamoelectric machine of the invention may vary widely in accordance with the installation and performance requirements, there follow by way of example only the design constants of the stator of Fig. 3 and the rotors of Figs. 4 and 6 designed to work therewith as a self-starting hysteresis motor:

Stator of Fig. 3

Rotor of Fig. 4

Shell 30, Alnico Il Outer diameter, 1.744 inches Inner diameter, 1.552 inches Core 3 I, SAE 1112 steel Outer diameter, 1.552 inches Pole width, 0.875 inch Inner diameter, 0.562 inch Air gap, 0.003 inch Rotor of Fig. 6

Shell 33, Laminated magnet steel-18% cobalt; 5% tungsten; 4% chromium; 0.75% carbon; balance, iron. l

Outer diameter, 1.7398 inches Inner diameter, 1.250 inches 26 gauge dynamo- The core 3| is illustrated as a four-pole: structure although it will be obvious that it may' be constructed with any number of poles to cor-- respond to the number of electrical poles of the The rotor also includes a supporting` shaft 32 of wear-resistant material, such as stain less steel, extending centrally through the core.4

of synchronism;

Core 313, Aluminum Outer diameter. 1.2.50 .inches Inner diameter, 0.562 inch Air gap, 0.0051 inch It is a common feature of the hysteresis dynamoelectric machines comprising the stators ci Figs. la, lb or liig. 5 and the rotors of Figs. la, 1b, Fig. 3 or Fig. 4 that the closed inner ends of the winding slots greatly reduce the parasitic hysteresis losses in the rotor otherwise occasioned by the pulsation in the flux produced by the open slots between the rotor teeth. With this construction it is preferable to reduce the air gap of the dynainoelectric machine to the minimum value allowed by manufacturing tolerances or other mechanical considerations. The radial thickness of the magnetic bridge at the inner ends ofthe winding slots is ypreferably made as small as consistent with structural rigidity. This construction is to be compared with that described in aforesaid Patent 2,328,743 involving a stator with open slots. As brought out in that patent, the construction illustrated and described therein is characterized by the fact that .there is an optimum air gap corresponding to the .value at which, for further increases in air gap, lthe rate of Iincrease of the copper losses due .to increased exciting current is equal to vthe rate oi decrease of parasitic hysteresis losses due to the tooth harmonics.

The power input-synchronizing Ator-que vcharacteristic of va motor comprising the stator of Fig. 3 'and the Arotor of Fig. 4 is represented by curve A ci Fig. 5 from which it is seen that, over the range oi data represented by :the curve, the synchronizing torque increases continuously and at a substantial rate with power input. At the point a of curve A, for a power input of 180 watts the synchronizing torque is 42 synchronous watts. Curve B o Fig. 5 represents a motor identical to that of curve A except that the stator bridge ring of Fig. 3 is -rnilled out to form slots 0.094 inch in width; that is to leave the'inner endsoi the winding slots substantially open in accordance with conventional design. `lt is seen that, for allvalues ofrpower input, the synchronizing torque is a minor fraction of that of the motor embodying the invention. YFor example, at a power input oi `130 watts,v the synchronizing torque is only 5.7synchronous watts. That is by the use of invention, the synchronizing torque is increased by a factor greaterthan '7. It is further to be noted from curve B that it becomes nearly asymptotic to thepower input axis for large values of power input so that further increases of power input do not increase the synchronizing torque appreciably. As is understood by those skilled in the art, the synchronizing torque ci a self-starting synchronous motor is an accepted factor of merit of the motor, as it represents the limiting load which the motor is able to synchronize, which is usually less than the pull-out torque, .that is the ,load which the motor will carry .without pulling. out this is .particularly true of motors having an effective salient-pole rotor construction, such as the rotor `oirFigfl In Fig. 6, curve C represents the power inputsynchronizing torqueoi a ,motor comprising the stator of Fig. 3 and the rotor ci Fig. 6, while curve i D represents the corresponding;characteristicof a motor comprising the statorof .-Fig.l 3 with the slots milled, as described above, andtlie-rotorof Fig. 6. It is seen that, '.onall-yalue orpower input. the synchronizing: torqnepf motor ern.-

bearing the invention is Substantially greater than .that Qf a. meier gmring the prior 'art stator with winding slots. With this'motor it was found that the limiting synchronizing torque was that at point of curve D corresponding/to a power input of approximately '77 watts, at which the motor developed a synchronizing torque of 22 synchronous watts. irrespective of how much the power input to the motor was increased, it still failed to synchronize for torques in excess of 22 synchronous watts. On the other hand, the NInotor embodying the invention had' the characteristic of increasing synchronizing torque Vfor all values of power input up to a value several times the rated capacity of the motor windings. rFor example, at a power input oi' 100 watts, the motor developed a synchonizing torque of 42.5 synchronous watts, approximately twice the syn.- chrcnizing torque developed by a motor with conventional stator slots.

Thus by the construction of the invention there is provided a self-starting hysteresis synchronous motor having a synchronizing torque of a higher order of magnitude than that of prior art motors oi the saine type. lt has been fiound that vthis characteristic also increases the sensitivity of the motor to control currents of relatively small phase-displacement or relatively small amplitude, or both, when the motor is operated "as a control cr torque motor below synchronous speed. Furthermore, tlie smooth adjacent cylindrical suriaces of the stator and motor impart to the motora virtually absolute uniform sensitivity in all rotor positions and increase the efficiency of the machine to a reduction in windage losses.

The hysteresis dynamoelectric machine of the invention `has a number of corollary advantages in addition to its improved electrical performance. Due to the smooth continuous adjacent cylindrical surfaces ci the stator and rotor, itis exceptionally quiet in operation, which is important in certain installations, such as in a driving motor-for a sound-translating apparatus.Y Further it permits the stator of a small non-commutated altrnngwurrent machine to be wound in aconventional armature winding machine, thus avoiding `the diilicult hand winding in a small tunnel of an armature with internal windingslo'ts. In addition, the bearings are supported directly from the core structure, whereby it constitutes,l a coinpletely shelf-supported, Seli-contained motor requiring no supporting housing. The motor may be supported froinits stator or fromeither or both bearings. Also, with this structure there are no limitations as to the number of'vwinding slotsthat can be provided, as there is n o' mechanical interference between the several motor windings. ln the construction of Figs. la and lb there is an added advantage that the armature tunnel and the bearing sleeves i5, i5 may be bored to the same diameter in one operation, ensuring'a high degree of .concentricity between thearmature land `rotor without expensive machining` operations, permitting the use. of the minimum A'air gap andf.ensuringv maximum magnetic efficiency and ka. maximum torque and power outputior any given size of motor. l

While there .have .beendescribed what are at present .considered .to be the .preierredlembodiments Aof thel invention, it .will be .apparent'to those skilled in vvthe artthat. various changes and ncdiiicationslinay be made therefin' without departingirom ,the...spirit tor scopey offthef inv-enton. v

I claim:

1. A hysteresis dynamoelectric machine including, cooperating stator and rotor members, one of said members comprising a magnetic core structure having a low conductivity to eddy currents and having a series of radially extending, angularly spaced winding slots and magnetic bridges for the ends thereof adjacent the other member and a polyphase distributed energizing winding disposed in said slots, the other of said members comprising a magnetic armature constructed at least in part of a magnetic material having a high hysteretic constant, said members having complementary cylindrical adjacent surfaces forming an air gap therebetween and having such relative diameters that said air gap is substantially the minimum permitted by manufacturing tolerances, and means for mounting said members for relative rotation.,

2. A hysteresis dynamoelectric machine including, cooperating stator and rotor members, one of said members comprising a magnetic core structure having a low conductivity to eddy currents and having a series of external radially extending Winding slots and a continuous inner bridge ring and a polyphase distributed energizing winding disposed in said slots, the other of said members comprising a magnetic armature constructed at least in part of a magnetic material having a high hysteretic constant, said members having complementary cylindrical adjacent surfaces forming an air gap therebetween and having such relative diameters that said air gap is substantially thc minimum permitted by manufacturing tolerances, and means for mounting said members for relative rotation.

3. A hysteresis dynamoelectric machine including, cooperating stator and rotor members, one of said members comprising a magnetic core structure having a low conductivity to eddy currents and having a series of radially extending, angularly spaced winding slots and magnetic bridges for the ends thereof adjacent the other member and a polyphase distributed energizing winding disposed in said slots, the other of said members comprising a magnetic armature including an annular shell of a magnetic material having a high hysteretic constant, said members having complementary cylindrical adjacent surfaces forming an air gap therebetween and having such relative diameters that said air gap is substantially the minimum permitted by manufacturing tolerances, and means for mounting said members for relative rotation.

4. A hysteresis dynamoelectric machine including, cooperating stator and rotor members, one of said members comprising a magnetic core structure having a low conductivity to eddy currents and having a series of radially extending, angularly spaced winding slots and magnetic bridges for the ends thereof adjacent the other member and a polyphase distributed energizing Winding disposed in said slots, the other of said members comprising a magnetic armature including an annular shell of a magnetic material having a high hysteretic constant and a central salient-pole core of high-permeability material, said members having complementary cylindrical adjacent surfaces forming an air gap therebetween and having such relative diameters that said air gap is substantially the minimum permitted by manufacturing tolerances, and means for mounting said members for relative rotation.

5. A hysteresis dynamoelectric machine including, cooperating stator and rotor members,

one of said members comprising a magnetic core structure having a low conductivity to eddy ourrents and having a series of radially extending, angularly spaced winding slots and magnetic bridges for the ends thereof adjacent the other member and a polyphase distributed energizing winding disposed in said slots, the other of said members comprising a magnetic armature including a relatively thin annular shell of a magnetic material having a high hysteretic constant and a central salient-pole core of high-permeability material, said members having complementary cylindrical adjacent surfaces forming an air gap therebetween and having such relative diameters that said air gap is substantially the minimum permitted by manufacturing tolerances, and means for mounting said members for relative rotation.

6. A hysteresis dynamoelectric machine including, cooperating stator-and rotor members, one of said members comprising a magnetic core structure having a low conductivity to eddy currents and having a series of radially extending, angularly spaced Winding slots and magnetic bridges for the ends thereof adjacent the other member and a polyphase distributed energizing winding disposed insaid slots, the other of said members comprising a magnetic armature including a relatively thick annular shell of a magnetic material having a high hysteretic constant and a central core of low-permeability material, said members having complementary cylindrical adjacent surfaces forming an air gap therebetween and having such relative diameters that said air gap is substantially the minimum permitted by manufacturing tolerances, and means for mounting said members for relative rotation.

7. A hysteresis dynamoelectric machine including, cooperating stator and rotor members, one of said members comprising a magnetic core structure having a low conductivity to eddy currents and having a series of radially extending, angularly spaced Winding slots and magnetic bridges for the ends thereof adiacent the other member and a polyphase distributed energizing winding disposed in said slots, the other of said members comprising aV magnetic armature constructed at least in part of a magnetic material having a high hysteretic constant, said members having complementary smooth continuous cylindrical adjacent surfaces forming an air gap therebetween and having such relative diameters that said air gap is substantially the minimum permitted by manufacturing tolerances, and means for mounting said members for relative rotation.

8. A hysteresis dynamoelectric machine including, cooperating stator and rotor members, one of said members comprising a magnetic core structure having a low conductivity to eddy currents and having a series of radially extending, angularly spaced winding slots and magnetic bridges for the ends thereof adjacent the other member and a polyphase distributed energizing winding disposed in said slots, the other of said members comprising a magnetic armature including an annular shell of a magnetic material having a high hysteretic constant, a supporting shaft of wear-resistant material extending centrally through said central core, said members having complementary cylindrical adjacent surfaces forming an air gap therebetween and having such relative diameters that said air gap is substantially the minimum permitted by manufacturing tolerances, and means for mounting said members for relative rotation. y .f

9. A hysteresis dynamoelectric machine including, cooperating stator and rotor members, one of said members comprising a magnetic core structure having a low conductivity to edd?,T currents and having a series of radially extending, angularly spaced winding slots and magnetic bridges for the ends thereof adjacent the other member and a polyphase distributed energizing winding disposed in said slots, the other of said members comprising a magnetic armature includingY a relatively thick annular shell of a magnetic material having a high hysteretic constant and a central core of low-permeability material, a supporting shaft of wear-resistant material eX- tending centrally through said central core, said members having complementary cylindrical adjacent surfaces forming an air gap therebetween and having such relative diameters that said air gap is substantially the minimum permitted by manufacturing tolerances, and means for mounting said members for relative rotation.

10. A hysteresis dynamcelectric machine including, cooperating stator and rotor members, said stator member comprising a magnetic core structure having a low conductivity to eddy currents and having a series of external radially extending, angularly spaced winding slots and an inner continuous magnetic bridge and a polyphase distributed energizing winding disposed in said slots, a magnetic yoke surrounding said core structure and winding, said rotor member comprising a magnetic armature constructed at least in part of a magnetic material having a high hysteretic constant, said members having complementary cylindrical adjacent surfaces forming an air gap therebetween and having such relative diameters that said air gap is substantially the minimum permitted by manufacturing tolerances, and means for mounting said members for relative rotation.

ll. A self-starting hysteresis synchronous motor comprising a stack of electrically insulated annular core laminations and one or more supporting bearing plates with external radial winding slots, a layer of thermoplastic adhesive material interposed between adjacent laminations and between said laminations and said plates constituting means for securing said laminations and plates together without substantially impairing their insulation to form a unitary core structure,

a polyphase distributed energizing winding disposed in said external slots, a magnetic yoke disposed about said core structure and said winding, a supporting bearing mounted from and supported solely by each plate, and a cooperating smooth cylindrical rotor disposed `within the bore of said core structure and supported in said bearings and constructed at least in part of a inagnetic material having a high hysteretic constant.

l2. A self-starting hysteresis synchronous motor comprising a stack of electrically insulated annular core laminations and a pair of supporting bearing plates with external radial winding slots, a layer of thermo-plastic adhesive material interposed between adjacent laminations and between said laminations and said plates constituting the sole means for securing said laminations and plates together without substantially imp-airing their insulation to form a unitary core structure, a pclyphase distributed energizing rwinding disposed in said external slots, a magnetic yoke disposed about said core structure and said winding, a supporting bearing mounted from and supported solely by each plate, and a cooperating rotor disposed within the bore of said core structure and supported in said bearings and including a non-magnetic central portion and a surrounding annular shell of an aluminumnichel-cobalt alloy.

i3. in an hysteresis dynamo electric machine, a wound stator having an uninterrupted cylindrical wall, `a rotor comprising an annulus of ferro-magnetic material of high coercivity and support means mounting said annulus for rotation, the surface of said annulus adjacent said stator and the surface of said uninterrupted cylindrical stator wall being as close together as machine tolerances permit, said support means for said annulus being of such character that magnetic flux flows circumierentially .around said annulus over a segment the length of which is more than twice the radial thickness of said annulus.

14. A hysteresis dynamoelectric machine having co-operating stator and rotor members, one of said members comprising a `tic core structure having a low conductivity te eddy currents and having a series of radially extending, angulariy spaced winding slots and magnetic bridges for the ends thereof adiacent the other member and a polyphase distributed energizing Winding disposed in said slots, the other of said members comprising a magnetic armature constructed at least in part of a magnetic material having a high hysteretic constant, said members having complementary cylindrical adjacent surfaces forming an air gap therebetween and havrelative diameters such that said is the order of 0.2 per cent. of the smaller diameter of said complementary cylindrical adjacent surfaces, and means for mounting said members for relative rotation.

i5. A hysteresis dynamoelectric machine having cci-operating stator and rotor members, one of said members comprising a magnetic cere structure having a low conductivity to eddy currents and having a series of radially extending, angularly spaced winding slots and magnetic bridges for the ends thereof adjacent the other member and a polyphase distributed energizing winding disposed in said slots, the other of said members comprising a magnetic armature constructed at least in part of a magnetic material having a high hysteretic constant, said members having complementary cylindrical adjacent surfaces forming an air gap therebetween and having relative diameters such that said gap is of the order of 0.063 inch, and means for mounting said members for relative rotation.

16. A hysteresis dynamoelectric machine having co-operating stator and rotor members, one of said members comprising a magnetic core structure having a low conductivity te eddy currents and having a series of radially extending, angularly spaced Winding slots and magnetic bridges for the ends thereof adjacent the other member and a polyphase distributed energizing winding disposed in said slots, the other ci said members comprising a magnetic armature hav-- ing an annular shell of material having a high hysteretic constant, said shell having a low circumferential reluctance relative to all other paths through and around said rotor causing substantially all of the stator magnetic to now circumferentially therearound, said mem'- bers having complementary cylindrical adjacent surfaces forming an air gap therebetween and having such relative diameters that said air is ci the order of 0.2 per cent, of the smaller of 13 said diameters, and means for mounting said members for relative rotation.

17. A hysteresis dynamoelectric machine having (so-operating stator and rotor members, one of said members comprising a magnetic core structure having a 10W conductivity to eddy currents and having a series of radially extending, angularly spaced winding slots and magnetic bridges for the ends thereof adjacent the other member and a polyphase distributed energizing Winding disposed in said slots, the other of said members comp-rising a magnetic armature having an annular shell of material having a high hysteretic constant, said shell having a loW circumferential reluctance relative to all other paths through and around said rotor causing substantially all of the stator magnetic uX to flow circumferentially therearound, said niembers having complementary cylindrical adjacent surfaces forming an air gap therebetween and having such relative diameters that said air gap is of the order of 0.003 inch, and means for mounting said members for relative rotation.

HERBERE1 C. ROTERS.

14 REFERENCES Crm1) The following references are of record in the le of this patent:

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